Electric control system for fuel-oil burners



Lf L. SCOTT ELECTRIC CONTROL SYSTEM FOR FUEL OIL BURNERS Filed May 31, 1924 ATTORNEY Patented oct. 5, 1926.

1,602,175. PATENT .'oEFicE.

LEwis I.. sco'rr, or sr. Louis, Missouni.

ELECTRIC CONTROL SYSTEM FOR FUEL-OIL BURNERS.

Application led May 31,

This invention relates to oil burning systems and particularly to a novel construc-Y tion and arrangement of an automatic electrici` mercury switch for controlling combustion. Y

One of the objects of the invention is to provide novel meansfor mounting a mercury tube of an electric switch in a manner to obviate the formation` of joints, which in time stick orcorrode. This object is effected byl mounting the tube on an armature which is, in turn, mounted on a flat spring, so that when the armature is attracted by electro-magnets,'the spring will yield to permit the tilting of the tube to cause the mercury therein 'to -flowfrom one end to the Another object of the invention is to provide'novel means for insuring that sufficient tilt shall be given to the mercury tube, in its actuation to close the switch, to insure that the' mercury will flow to the end of the tubecontaining 'the contact wires.

Another object of. the invention relates to mea-ns for actuating an armature by electro-magnets andatrthe same time automatically opening or closing a mechanical electric switch without subjecting the switch member to vibration, which follows from the i ation of the switch unreliable.

" ciiic embodiment ofmy invention, the aiA usual arrangement i-n which a switch meinber is' directly attracted by electro-magnets" energized from an alternating current, whereby' arcing occurs at thecontacts, caus-. ing them to burn away,.rendering the oper-l In the spemature carries the mercury tube of a main electric control switch.

Another v object of the invention resides in the novel manner of mounting the inercury tube for movement under -the influence of electro-magnets',`whereby should the support for the tube break, the tube will fall into position to cause the mercury to iiow tothe end of the tube-opposite to that containing the contact `wires and thus shut off place of combustion.

A-still further object of the invention 're-- sides in'theprovision of a safety-devicecomprising .an electric .circuit for cont-rolling the operation of electrical devices which in turn control the initiation and maintenance of combustion, a switch in said circuit nor-l mally open and automatic means for actu- 1924. Serial No. 717,189.

atin the switch controlled by combustion con itions and operating, upon combustion being established, vto close said switch to permit the continuance of combustion and, upon failure of combustion to occur, to maintain said switch open and thereby render said electrical devices inoperative.

In the preferred embodiment of my in vention shown in the drawings, this safety device is in the form of a thermostatic switch which -is vadapted to be moved to close the control circuit under heat of combustion and to hold the lswitch open when there is no heat. The invention, however, is not limited to this particular means for effecting the operationof this safety device.

Other objects of the invention relate to details of construction and to combinations and arrangements of parts hereinafter described and pointed vout-in the claims.

The invention is illustrated in the accompanying drawing in which the view is a diagrammatic view of a'fuelburning system having my control apparatus applied thereto, the switch board being shown in front elevation andthe furnace and.' connected parts being shown -in sectionalv plan. Referring now to the drawings, the numeral 1 indicates a board of insulating material, on which the control switches are mounted, and which switches will now be' described. The numeral 2 indicates a glass tube which is partly illed with mercury and which has a pair of electric contacts 3-3 at one end, to which are connected the ends of iexible conductors 4, which at their other ends are connected to binding posts 5. f

tube 2 is mounted in clips 6 which, in turn,

are mounted on an armature 7. Secured to the armature 7 is a fiat or leaf spring 8, one

-end of which is secured -to a bracket 9 mounted on'the board 1. The armature 7 is adapted to be acted'on by the electromagnets'10-11,and when such action takes place, the tube 2 will tilt to theright and cause .the mercury therein to flow to the right-hand end'of the tube and close the electric contacts 3. -In this movement,' the spring 8 yields to `permit the tilting of the tube as described. It will'be observed that the magnets are inclined slightly to' the' right. The arrangement described is such asto secure a sucient tilt of the tube to 5 down the outer end ofthe armature, causing the spring 8 to buckle slightly, giving additional tilt t the mercury tube. In some cases where the apparatus was not properly leveled, it would be found implos-4 Nt sible for this mercury tube to properly Opf crate because of the small angle .through which it works.

When the magnets are de-energlzed, the spring 8 has suflicient power to tilt the tube l5 2 tothe left, or into the position shown in the drawing. The actuation of the armature 7 is used, according to my invention, to automatically and indirectly operate an electric switch in a circuit to be presently 'described To this end, there is secured on the rear end of the armature 7 an arm 12, which normally engages the free end of a spring arm-13, which, at its other end, 1n the drawing the lower end, is secured to, or forms part of, a

conducting plate 14, mounted on the board 1.

The spring arm 13 constitutes a movable switch member and has mounted thereon, near its free end, a contact member or switch 15, which .is adapted to make and break contact with the end of an adjustable contact member 16, which is mounted in a conducting plate or bracket p 17a, secured on the board 1.

The spring arm 13 tends normally to move the contact 15 into engagement with the en'd of contact 16, but is held from such movement by the arm 12 on the armature 7l lVhen the magnets 10-11 are energized and the armature 7 pulled downward, the'arm 12 will be moved away from the free end of the spring arm 13, andthe latter will move to the left, as shown 1n thefdraw1ngs, to bringthe contact 15 into engagement. with the contact 16. When the armature 7 is` raised by spring 8, the arm 12 again moves the switch member 13 to the right to break.

connection between the contacts 15 and 16.

From the above described arrangement, it

will be seen that the switch member 13, while controlled in its movement bythe armature 7, is not subject to vibrationas; when the contacts 15 ,and 16 are closed, the arm 12 will be out of engagement with the end of the switch member 13, and while the armature 7 will, or may, vibrate, and will certainly do so if the magnets are energized by alternating current, such vibration has no effect upon said switch member 13.

The numerals 17 and 18 indicate the main electric wires of which the wire 17 runs to a motor 19 and is connected by branch wires 20 and 21 to one end vof primary coils 22 and 23, respectively, of transformers 24 and 25. The wire 18 leads to the binding post 5 and through the contacts 3-3 and the second binding post 5 to the motor 19. Branch transformer 24, a wire 28 leads to an ordinary spark coil 29, and from this spark coil a wire 30 leadsto a spark plug 31. The ground connectionis indicated at 32. The numeral 33 indicates a room thermostat which controls the current to the magnets 10-11 according to the temperature of the roomfin which said thermostat is located. 4Currentfor the room thermostat circuit is supplied by the low-voltage side 34 of the transformer 25,

J A wire 35 from the low-voltage side of transformer 24 runs to a spring contact member 36, whichco-operates with an adjustable contact member 37.v The numeral 38 indicates a strip of thermostatic metal,

which at its upper'end is secured to a con` ducting plate 39 mounted on the board 1 and grounded at 40, and its lower end is provided with a Contact 41 which is adapted, when the strip of thermostatic metal 38 is cold, to engage the spring contact member 36 `and force 1t ultimately into engagement with the contact member 37. A wire 38a connects the thermostatic metal 38 with the low-voltage side of transformer 25. When the contact 41 engages the Contact 36, the current to lthe spark coil- 29 wiltbe completed through the strip of thiermostatic metal 38 which isvgrounded at 40, one side of the spark coil 29 being` also grounded., at 32, as previously stated.4

lt is necessary that the mercury tube 2 be tilted tothe right before current will flow to motor 14 and transformer 24.

Wound about the thermostatic strip of metal 38 is a coil 42 which is for the purpose of heating said thermostatic metal and causing it to move to the right to onen certain circuits which will be described in ldetail later. The coil 42 is connected in parallel withthe coils 43 of the magnets 10-11.

' The wire 44- of .transformer 25 runs to coil 42, and the other wire 45 from said transformer runs through room thermostat 33 to one end of the coils 43 of magnets 10-11.

ico

The other end 'of the coils .43 is connected to the conducting plate 17, previously referred to, and from this plate a wire 46 leads to a conducting plate 47 yon which the adjustable contact 37 is mounted. A wire y 48 runs from the'switch member 13 to the ground'connection 40, but has interposed in its length a thermostatic switch comprising a thermostatic barv 49 and a contact screw 50. The thermostatic bar is located in suitable proximity to the burner 51 which supplies ignited fuel to the furnace 52 to be effected by the heat thereof, and when heated, it acts to close a contact between itself and the screw 50 to establish the circuit over the line wire 48. Theelectric motor.19 .operates the air blower53 and a .fuel pump-54. A suction pipe 55 runs to a' fuel-.tank (not shown) and thel discharge pipe-56 is con-- nected to a fuel spray.r nozzle 57 lVhen the motor 19 starts, fuel. is pumped to spray nozzle 57 andair. is furnished. to the fuel spray by the blower wheel 53,1and said fuel is ignited by the spark plug 31.

Assuming the mercury tube 2 isl in the position shown and that the contacts 37, 36 and 41 are alll in proper engagement with each other, upon closing of the thermo-static switch 33, current vwill iiow .from transformer through .the magnet coils 43. through contacts 37 ,u 36 and 41, andA .through the vcoil 42 back to the transformer25. The instant that current ows .through the magnetcoils 43, the armature .7 will be attracted by the magnets 10 and 11 and the tube 2 will v tilt to the right, causing the mercury therein to flow to thev end .ofthe tubecontaining I thecontacts 3 and through saidcontacts to close the circuit to motor 19 and transformer 24. This transformer will furnish current to the spark..coil.29, as before described. -In the movement of the armature under the 'attraction of the magnets 10 and 11, the .said armature will first engagethe end of magnet 10 and thenitsouter end will be drawn downward by magnet 11, causing the spring 8 to slightly. buckle, a nd insuring a sufiicient tilt of the tube 2 to cause the mer-' cury therein to flow to thel endcontaining the contacts 3. -hen the armature 7 isfattracted by the magnets, the arm 12 thereon will release the spring switch .member 13 and permit it to engage the l.contact l16 whereby a parallel electrlc current from the magnet coils 43 to the coil 42- will beestablished overthe wire48 as'soon as the` heat of the burner actuates the thermostatic bar" 49 to make engagement' with contact 50. As soon as the thermostatic strip 38 has been heated'by coil 42 to the proper temperature, said strip. will move to. the right and Open the contacts 37,36 and 41. :That is to say',

when the thermostatic stripmoves to the right, the spring Contact member 36 will also move to the right a small. amount so as to be out of engagement with thel .end of the screv1 contact 37. Theo ening of these contacts 37 and 36 breaks. .t e-circuit of one. of the parallel circuits to magnet .coils 43j and coil'42, the circuit thus brokenbeing that carrid over the wire46.. .The opening of contac s 4 1 and .36. breaks .the circuitto. the spark coil 29 over the wire..35. It willl be seen,'howev er, that .currentcontinues toI flow throughcoils 4 2 and 43.because. .of the'. circuit established -by contact of theswitch member'13 with the contact 16 Vas before, described. If the circuit to the room thermostat is broken, or if the main line currentis shut olf, 'no current will .flow through' .the

magnet. coi1s'f43 or :coil 42 and .the mercury tube 2 will. instantly: tilt .to `the left under the iniuence of spring 8, `and the circuitxto motor 19 and ltransformer 24 will be instantly broken. The immediate closingof the room thermostat circuit, or of the'main line circuit, will not start the -motor -until the thermostatic strip 38 has vbeen cooled down suiiciently so that it will move to the -left'and establish the contacts at 41 and 36 and then at 36 and 37. "With this arrangement,l it is impossible at any timeto turn on lthe motor 19 until the circuit yto sparkcoil 29 :ha-sheen closed by contacts 41 and v36. I usually set the thermostaticstrip 38 sothat it will closecontacts 36 and37- in from one to two Vlminutes .aftercurrent is' shut 0H from coil 42. .This feature of the invention, however,is claimed in my pen-ding lapplication Serial Number' 602,291, filed vl\lovember'20,

1922,.and is only brieiy referred'to fherein to make the general construction and operation ofthe device clear. l

The electric safety feature afforded bythe thermostatic switch 49, 50 is an important 1 feature of the inventionand is distinguished by the fact that this switch is closed by heat from the fire and is `open when therev is no heat; therefore, with t is arrangement, the

turning on I of :the :burner .depends .on hav inggthe-switch closed, andthe turning off-of the burner dependsvupon having the switch open. This Vyieldsfpthe maximum .of safety 'as .i .compared :to fan; Velectric safetydevice where, the' tunning` off, "of -the burner. depends -on .the making of the Scircuit rather than on thebreaking thereof.

.. In order thatthe operation and the advan'- tages y-of this; safety device maybe :understood, let it be assumed that when the room thermostat circuit was vclosed and vthe" cir# cuit to the motor established, the sparkv plug failed to operate or, operating, failed to ignite the fuell; Under l these circumstances,v

the thermostatic bar49 would remain out ofcont'act with thescrewl 50 and no circuit will have. been established .over the wire 48 bythe release of the switch member 13 eected by the attraction of the armature 7. -As soon, v

therefore, as thecoil 42 had heated the thermostatic bar-38 to causeit to break the con# tacts at 37, 3 6 and 4 1, nocurrent would pass through the coils 43, the circuit over the wire 48 .being open, and hence the .magnets would be de-energizedand.thefspring 18.

would'.l cause the mercury tube 2.xto til't, and

break the circuitito the motor .'19 Thus, it

willbe.- seen that .when the:room thermostat. circuit I is closed, if theivfuelffailstosignite, for anycause, fthe. electrical controlf -system: described will automaticallycausa the operation -of thei'notor to cease-after a-zbrief yins. tervalof-time. v Iclaim: 1.v In. an. .electric .control .systenrcfoinfoil after to open the circuit to said electricallyoperated means, a'safety device for. controlling the 4operation of said electrically-operated means after the circuit thereto has been broken comprising an electric circuit including said electrically-operated means, and an automatic Switch in said circuit normal.- ly open and operating, upo: 'establishment of combustion, to close `before said iirst namedlswitch opens.

2. In 'an electric control system for oil burners, in combination with electrically-operated means for initiating and maintaining combustion, a safety-device for controlling the operation of said electrically-operated means comprising an electric circuit including said electrically-operated means, an automatic device controlling the operation of said electrically-operated means which is nori mally in position to lpermit the starting thereof,` an automatic safety-switch responsiveto combustion conditions for controlling the operation of said electrically-operated means and maintaining the circuit thereto during the running period of said electrically-operated means, said automatic safety ,switch being adapted to co-operate, when closed, with said automatic device to permit the-burner to continue tooperate if combusg tion ltakes place, and, when open,5to,I shut olthe `burner when there is no combustion, said automatic safety -switch being normal- 1y open and operating upon, the i establishment ofcombustion to close, whereby upon the `failure of combustion, the failure of saidA 1 switch to close will permit` the automatic device to render said electrically-operated means inoperative: I A.

3. In an electric -control system for ioil burners, in lcombination with electrically-operatedmeans for initiating and maintaining combustion, a circuit thereforcontroll'ed by Y a room thermostat, automatic means operating, after` closing said circuit, to break the circuit to said el'trically-o'peratedmeans," and a safety device' for controlling the operation of said electrically-operated'means after the' ci'rcuit thereto vhas vbeen broken, comprisin' .a second electric circuit including said e ectrically-operated means, and estabilished in part by the initial actuation of the latten.. and an automatic vswitch in said second circuit normally open-`and operating,

upon establishment of combustion, to close,

'-,wherebyyupon failure :fof combustion, the

failure ofv said .circuit to close will render saidelectrically-operated means inoperative.

trically-operated Adevices fer-"effecting the operation of thesame, an electric circuit including said devices, electrically-operated means controlling the making and breaking the circuit to said electrically-operated means 1 after it has been established by the operation of the room thermostat, a third circuit for controlling said electrically-operated means and established in part by the-actuation of the latter to close the' first named circuit, and automatic means responsive to combustion conditions normally holding said third circuit pen and operating, upon establishment of combustion, to close the same, whereby upon the failure 'of combustion, the failure `of saidl automatic means to close said last named circuit will render the system inoperative. In an electric control system for oil burners, in combination with a burner, electrically-operated devices for effecting the operation of the same, a circuit therefor, a main control switch governing the circuit to said devices, an automatic switch which controls the operation of said main4 control switch, a `vparallel circuit which connects to said automatic switch. and which is established in part by the closing of said main control switch, .and when established, controlling the operation thereof, and a thermostatic switch located in proximity. to the burner and actuated to be closed by the heat thereof -and to open when there is no heat whereby, upon 'failure of ignition upon operation of the main control switch, the automatic switch will cause the main control switch to break the circuit to said devices.

6. In yan electric control system for oil burners, in combination withelectricallyoperated means for initiating and maintain- `ing combustion, a safety device for controlling thel operation of said electrically-operatedfmean's, comprising an electric circuit inctdingi said electrically-operated means, an electrically-heated thermostatic device which is'normally in osition to permit the starting-of the electrically-operated means,

an automatic switch in the electric circuit and which is adapted to co-operate with said electrically-heated thermostatic device either to permit the burner to'continue to operate iff combustion takes place .orto shut off the burner if there is no com ustion, said auto- 'mati'cfswitch being normally open and operating upon the establishment of combustion to close, whereb upon the failure of combustion, the fai ure of said switch to close will permit the electrically-heated thermostatic device to render said `electrically- I i operated means-inoperative. j 4. In an electrlc control system for oil 05k burners, in VIcombinationfwith a burner, 'elecoperation of the same, a main control switch governing the circuit to said devices, an electro-magnet for actuating said switch, an electric circuit including said magnet, automatic means operating to establish said circuit to actuate said switch and thereafter to break the circuit, and safety means'for controlling said switch comprising a parallel circuit including said magnet and having a thermostaticswitch located therein in proximity tothe burner and adaptcdzt'o be closed by the heat thereof and to open when there is no heat, whereby, after the main switch has been closed to establish thetcircuit to said devices', should thefuel fail to ignite, when the. first named circuit to said magnet is broken, the magnetl will be (le-energized by failure of the thermostatic switch to close the parallel circuit and said control switch ywill open to break the circuit to said devices.

v8. In an velectric .control system for oil burners, in combination with 'aburner, electrically-operated .devices operation of the same, a main control vswitch for effecting the governing the circuit tofsaiddevices, an electro-magnet for actuating said swltch, an automatlc swltch 1n sa1d electro-magnet circuit which is normally closed and which isadaptedv to automatically open in. a short* time after said main control switch is closed,

andv safety means for controlling saidymain switch comprising a parallel .circuit includswitch located therein in proximityv to ythe burner and adapted to be vclosed by the heat thereof and to open when there is no -heat, whereby, after -the-main switchA has been closed toestablish the circuit .to said devices,

ing said magnet and having a thermostatic should the fuel fail to ignite, when the cir- 'cuit to said magnet' is broken, the magnet will be de-energizedbythe failure ofthe thermostatic switch to close thelparallelcircuit, and said main control switch will open to brealz'the circuit to said devices.-

In testimony whereof, vI have hereunto set myv hand. 

